Methods and apparatus for examining tissue in vivo using the decay characteristics of scattered electromagnetic radiation

For use in method of spectroscopic examination of a substance that lies in a path between an optical input port and an optical detection port of a spectrophotometer, the substance having scattering and absorptive properties, the method comprising the time-dependent steps of:

• (a) introducing to the scattering and absorptive substance, at said input port, at least one selected wavelength of visible or near infrared electromagnetic radiation pulse having an input waveform of duration of a nanosecond or less,
• (b) detecting over time, at said detection port, at said selected wavelength, radiation of a pulse waveform formed by photons that have migrated over scatter paths in said scattering and absorptive substance from the input port located several centimeters from the detection port,
• (c) storing over time signals corresponding to detected photons that have migrated over said scatter paths and representing a detected radiation pulse waveform, change in the detected radiation pulse waveform from the input pulse waveform being attributable to the absorptive and scattering properties of said substance in paths through which photons said radiation migrate, and
• (d) determining the effective length of said paths over which said detected radiation migrates, said length being dependent on degree of scattering and absorption in the light-scattering substance, by determining change between the input pulse waveform and the detected pulse waveform measured over time for said wavelength.

A method of spectroscopic examination of biological tissue of a subject lying between an optical input port and an optical detection port of a spectrophotometer applied to the subject, optical pathlength between said ports being dependent upon scattering and absorptive properties of the tissue, the method comprising the steps of:

• (a) introducing into the tissue at the input port a pulse having an input waveform of duration of a nanosecond or less of a selected wavelength of visible or near infrared radiation,
• (b) detecting over time, at the detection port, radiation of a pulse waveform formed by photons that have migrated over scatter oaths in the tissue from the input port located several centimeters from the detection port,
• (c) storing over time signals corresponding to detected photons that have migrated over said scatter paths and representing a detected pulse waveform,
• (d) determining change in shape of the detected pulse waveform at said wavelength relative to the input pulse waveform, and
• (e) based upon said change, determining a desired spectroscopic parameter related to a constituent of the tissue in which said radiation has migrated.

A method of spectroscopic examination of biological tissue of a subject lying between an optical input port and an optical detection port of a spectrophotometer applied to the subject, an optical pathlength between said ports being determined by scattering and absorptive properties of the tissue, the method comprising the steps of:

• (a) introducing into the tissue at the input port a pulse having an input waveform of duration of a nanosecond or less of a selected wavelength of visible or near infrared radiation,
• (b) detecting over time, at the detection port, radiation of a pulse waveform formed by photons that have migrated over scatter paths in the tissue from the input port located several centimeters from the detection port,
• (c) storing over time signals corresponding to detected photons that have migrated over said scatter paths and representing a detected pulse waveform,
• (d) determining change in shape of the detected pulse waveform, at said wavelength, relative to the input pulse waveform, said change being attributable to said absorptive and scatter properties of the tissue in which the radiation migrates, and
• (e) based upon said change in shape of the detected pulse waveform, characterizing the tissue in which the radiation migrated.